The theory and practice of transmitting data via optical waveguide fibers is well-known in the communications industry. Such fibers, usually composed of a glass or other transparent, refractory material, serve advantageously as a medium for guiding coherent light expressing data over long distances. Guided transmission of propagating light waves has been made possible by embedding or surrounding the glass material of a given refractive index with a different material having a lower refractive index. Relatively recent innovations in the manufacturing of fiber optic cables and improvements in the compositions utilized, such as fused silica doped with titania, have resulted in tighter control of the angles of incidence at which light waves propagate within the fibers to ameliorate the inefficient "bouncing" profile exhibited by the wave propagation. Thus, greater integrity of transmitted discretized data pulses has been achieved.
Fiber optic cables can be produced in a ribbonized configuration wherein a row of drawn optical fibers are grouped in parallel with each other and clothed in a mylar matrix. In the United States, the twelve-fiber ribbon has become the standard, while in European and Asian countries the standard is between four and twenty-four fibers per ribbon. For service and maintenance purposes, it often becomes necessary to perform splicing and termination operations on individual or discrete fibers of the optical fiber ribbon. Before performing such operations on a particular fiber within the optical fiber ribbon, it may become necessary to access a discrete fiber by removing it from the optical ribbon without disturbing or damaging the other fibers. Various strategies for splitting or breaking out fibers have been developed, all of which are considered to be deficient.
One frequently used method for breaking out discrete fibers has been to employ chemicals such as butyl-ethyl acetates to degrade the matrix. These chemicals require careful handling by technicians as they are biologically injurious. Moreover, the chemicals are expensive, have limited shelf life, and pose environmental hazards.
Another method has required the use of scratching means to produce scores on the surface of the matrix prior to breaking out the fibers. For example, U.S. Pat. No. 5,524,166, issued to Osaka et al., discloses a tool for separating a multi-core ribbon. The tool uses a plurality of pins to form scratches on the matrix by clamping down on the ribbon and pulling the ribbon along the pins in the longitudinal direction of the fibers. The flats of the ribbon are then sandwiched between alternating, opposing shearing force application members which, when driven toward the ribbon, induce breaks in the matrix along the scratch lines to separate out the fibers. A ribbon may be split in this manner into a number of divisional states--e.g., in a twelve-fiber ribbon all twelve fibers may be separated, or three groups of four fibers, or four groups of three fibers, etc. However, realization of the desired divisional state requires selecting the appropriate pin configuration, and when a different divisional state is sought the pin configuration must be modified.
The several embodiments depicted in Osaka et al., contemplate an excessive number of complex, bulky machined components and an excessive number of method steps. In addition, the use of scratching pins carries an unacceptable risk of damaging the optical fibers in the matrix. It is well known to a skilled professional within the field that optical fibers are extremely sensitive to scratching even when the scratching does not break the fibers. Even a slight scratch or other defect on the surface of an optical fiber may create a number of unwanted conditions, such as dislocations in the fiber's crystalline structure and/or a change in the refractive index contrast. These and other adverse conditions can result in inferior transmission of data. For even minimal scratching on the surface of optical fibers may produce a scattering effect on light waves propagating therethrough, thereby corrupting the data being transmitted.
The deficiencies of such prior art embodiments are also evident in U.S. Pat. No. 4,046,298, issued to Schroeder, Jr., which discloses a relatively large apparatus employing among other things a combination of rotating wheels and shafts, a micrometer, adjustment assemblies, and scratching pins.
The technology relating to splitting of ribbonized electrical conduits similarly does not aid in solving the problem of splitting ribbonized fiber optic cables, because such technology has likewise not been sufficiently sensitive to the deleterious effects of scratching caused by cutting and scoring apparatus on optical fibers as compared with electrical conductors. Imperfections created on the surface of electrically conductive materials, such as copper, aluminum, silver, gold and platinum, do not impair the function of the conductor to any appreciable degree. Such conductors are quite ductile and malleable, and retain these properties after being subject to splitting operations. By contrast, optical fibers are brittle and exquisitely prone to breaking. Moreover, there has been no need to focus on the problem of scratching in the electrical conductor art because scratching does not impair the conductive function. For example, scratching usually does not change the cross-sectional area of electrical conductors to an extent significant enough to alter resistivity or rate of heat dissipation.
Accordingly, it is an object of the present invention to provide a simple, economical, non-chemical solution to the problem of breaking out discrete optical fibers from optical fiber ribbons and of separating those ribbons into subgroups of fibers. In furtherance of this object, preferred embodiments of the present invention will now be described.